1. Field of the Invention
The present invention relates to measuring the contour of a surface from a position located remotely from that surface and particularly to determining the profile of the surface of charge material which has been deposited on the hearth of a furnace. More specifically, this invention is directed to apparatus which employs a beam of radiant energy, electromagnetic energy in the radio frequency spectrum for example, to determine the profile of the surface of the burden in a shaft furnace. Accordingly, the general objects of the present invention are to provide novel and improved method and apparatus of such character.
2. Description of the Prior Art
It is well known that proper exercise and control over the profile of the charge on the hearth of a blast furnace is essential to maximizing the efficiency of operation of the furnace. Obviously, in order to control charge profile, means must be provided for determining the contour of the surface of the charge at least on a periodic basis during the furnace charging procedure. Devices for making such measurements are known in the art as profilometers. The prior art profilometers may be classified generally as either being of the mechanical probe type or the radiant energy type. The early mechanical probe type profilometers were capable of making a measurement at only a single point. Improved mechanical probe type profilometers enable the shifting of that single point of contact with the surface of the charge. Nevertheless, for sufficient information to be collected so as to enable the charge profile to be determined with the requisite accuracy, a large number of individual measurements are required thus making the task of determining the charge profile a time-consuming endeavor. Examples of mechanical probe type profilometers of modern design may be found in U.S. Pat. Nos. 3,905,239 and 4,094,494. The profilometer of U.S. Pat. No. 4,094,494 is designed for use with a furnace charging installation of the type which is known in the art as a "bell-less top" or a "coneless throat." Such a charging installation, which employs a rotatable and angularly adjustable charge distribution chute positioned within the furnace, is shown and described in U.S. Pat. No. 3,693,812. The apparatus of U.S. Pat. No. 3,693,812 has the advantage of allowing excercise of a high degree of control over the charge profile when sufficient surface contour information is available.
Profilometers of the radiant energy type may be based upon radar technology and include means for transmitting electromagnetic energy to the charge surface and receiving energy reflected from the charge surface. A radar profilometer is described in Luxembourg Pat. No. 70310. Profilometers which employ a beam of radiant energy theoretically constitute a technical advance over mechanical probes since they offer the ability of collecting the requisite contour information rapidly and are suited for automated control. The information derived from the energy reflected from the charge surface and received back at the profilometer antenna, whether the profilometer is operated in accordance with a predetermined schedule or programmed with the charge distribution device, may be employed to control the motion of a charge distribution chute of a furnace charging installation of the type shown in U.S. Pat. No. 3,693,812.
Profilometers of the radiant energy type, for example those which operate on the principles of radar, present a number of operating problems which have previously prevented the use of these measuring devices and techniques on a commercial scale. By way of example, in order to perform maintenance operations on those components of the profilometer which must be directly exposed to the furnace operating environment during the taking of surface contour measurements, means must be provided for selectively hermetically isolating these components from the interior of the furnace. This hermetic isolation must be accomplished without impeding the operation of the furnace. Considering a radar profilometer, which would typically employ an antenna comprising a parabolic reflector having a diameter on the order of 300 mm, the aperture which must be provided in the furnace wall to enable removal of the antenna for servicing is quite large. This aperture must be hermetically closed without interfering with either the operation of the profilometer or the furnace and it is to be noted that the problem of providing such a hermetic seal is complicated by the fact that modern blast furnaces operate with high pressures.
A second, closely related problem resides in maintaining the profilometer in the operative state. The conditions within the furnace constitute an exceedingly harsh operating environment and a coating of particulate matter rapidly forms on all exposed surfaces located within this environment. The deposits which would form on the parabolic reflector of a radar antenna would, within a few days, render a radar profilometer inoperative.